package com.habitsoft.glassfish.dashboard.server;

import java.io.IOException;
import java.io.Reader;

/**
 * Rehash of BufferedReader that uses glassfish' log convention for log lines
 * handling instead of newlines.
 * 
 * i.e. each call to readLine() returns the next [#| ... |#] part instead
 * of the next newline-terminated part.
 * 
 * This code is based on the source code for BufferedReader from Sun.
 * 
 */
public class LogReader extends Reader {

    private Reader in;

    private char cb[];
    private int nChars, nextChar;

    private static final int INVALIDATED = -2;
    private static final int UNMARKED = -1;
    private int markedChar = UNMARKED;
    private int readAheadLimit = 0; /* Valid only when markedChar > 0 */

    /** If the next character is a line feed, skip it */
    private boolean skipLF = false;

    /** The skipLF flag when the mark was set */
    private boolean markedSkipLF = false;

    private static int defaultCharBufferSize = 8192;
    private static int defaultExpectedLineLength = 80;

    /**
     * Creates a buffering character-input stream that uses an input buffer of the specified size.
     * 
     * @param in
     *            A Reader
     * @param sz
     *            Input-buffer size
     * 
     * @exception IllegalArgumentException
     *                If sz is <= 0
     */
    public LogReader(Reader in, int sz) {
        super(in);
        if (sz <= 0)
            throw new IllegalArgumentException("Buffer size <= 0");
        this.in = in;
        cb = new char[sz];
        nextChar = nChars = 0;
    }

    /**
     * Creates a buffering character-input stream that uses a default-sized input buffer.
     * 
     * @param in
     *            A Reader
     */
    public LogReader(Reader in) {
        this(in, defaultCharBufferSize);
    }

    /** Checks to make sure that the stream has not been closed */
    private void ensureOpen() throws IOException {
        if (in == null)
            throw new IOException("Stream closed");
    }

    /**
     * Fills the input buffer, taking the mark into account if it is valid.
     */
    private void fill() throws IOException {
        int dst;
        if (markedChar <= UNMARKED) {
            /* No mark */
            dst = 0;
        } else {
            /* Marked */
            int delta = nextChar - markedChar;
            if (delta >= readAheadLimit) {
                /* Gone past read-ahead limit: Invalidate mark */
                markedChar = INVALIDATED;
                readAheadLimit = 0;
                dst = 0;
            } else {
                if (readAheadLimit <= cb.length) {
                    /* Shuffle in the current buffer */
                    System.arraycopy(cb, markedChar, cb, 0, delta);
                    markedChar = 0;
                    dst = delta;
                } else {
                    /* Reallocate buffer to accommodate read-ahead limit */
                    char ncb[] = new char[readAheadLimit];
                    System.arraycopy(cb, markedChar, ncb, 0, delta);
                    cb = ncb;
                    markedChar = 0;
                    dst = delta;
                }
                nextChar = nChars = delta;
            }
        }

        int n;
        do {
            n = in.read(cb, dst, cb.length - dst);
        } while (n == 0);
        if (n > 0) {
            nChars = dst + n;
            nextChar = dst;
        }
    }

    /**
     * Reads a single character.
     * 
     * @return The character read, as an integer in the range 0 to 65535 (<tt>0x00-0xffff</tt>), or
     *         -1 if the end of the stream has been reached
     * @exception IOException
     *                If an I/O error occurs
     */
    public int read() throws IOException {
        synchronized (lock) {
            ensureOpen();
            for (;;) {
                if (nextChar >= nChars) {
                    fill();
                    if (nextChar >= nChars)
                        return -1;
                }
                if (skipLF) {
                    skipLF = false;
                    if (cb[nextChar] == '\n') {
                        nextChar++;
                        continue;
                    }
                }
                return cb[nextChar++];
            }
        }
    }

    /**
     * Reads characters into a portion of an array, reading from the underlying stream if necessary.
     */
    private int read1(char[] cbuf, int off, int len) throws IOException {
        if (nextChar >= nChars) {
            /*
             * If the requested length is at least as large as the buffer, and if there is no
             * mark/reset activity, and if line feeds are not being skipped, do not bother to copy
             * the characters into the local buffer. In this way buffered streams will cascade
             * harmlessly.
             */
            if (len >= cb.length && markedChar <= UNMARKED && !skipLF) {
                return in.read(cbuf, off, len);
            }
            fill();
        }
        if (nextChar >= nChars)
            return -1;
        if (skipLF) {
            skipLF = false;
            if (cb[nextChar] == '\n') {
                nextChar++;
                if (nextChar >= nChars)
                    fill();
                if (nextChar >= nChars)
                    return -1;
            }
        }
        int n = Math.min(len, nChars - nextChar);
        System.arraycopy(cb, nextChar, cbuf, off, n);
        nextChar += n;
        return n;
    }

    /**
     * Reads characters into a portion of an array.
     * 
     * <p>
     * This method implements the general contract of the corresponding
     * <code>{@link Reader#read(char[], int, int) read}</code> method of the
     * <code>{@link Reader}</code> class. As an additional convenience, it attempts to read as many
     * characters as possible by repeatedly invoking the <code>read</code> method of the underlying
     * stream. This iterated <code>read</code> continues until one of the following conditions
     * becomes true:
     * <ul>
     * 
     * <li>The specified number of characters have been read,
     * 
     * <li>The <code>read</code> method of the underlying stream returns <code>-1</code>, indicating
     * end-of-file, or
     * 
     * <li>The <code>ready</code> method of the underlying stream returns <code>false</code>,
     * indicating that further input requests would block.
     * 
     * </ul>
     * If the first <code>read</code> on the underlying stream returns <code>-1</code> to indicate
     * end-of-file then this method returns <code>-1</code>. Otherwise this method returns the
     * number of characters actually read.
     * 
     * <p>
     * Subclasses of this class are encouraged, but not required, to attempt to read as many
     * characters as possible in the same fashion.
     * 
     * <p>
     * Ordinarily this method takes characters from this stream's character buffer, filling it from
     * the underlying stream as necessary. If, however, the buffer is empty, the mark is not valid,
     * and the requested length is at least as large as the buffer, then this method will read
     * characters directly from the underlying stream into the given array. Thus redundant
     * <code>BufferedReader</code>s will not copy data unnecessarily.
     * 
     * @param cbuf
     *            Destination buffer
     * @param off
     *            Offset at which to start storing characters
     * @param len
     *            Maximum number of characters to read
     * 
     * @return The number of characters read, or -1 if the end of the stream has been reached
     * 
     * @exception IOException
     *                If an I/O error occurs
     */
    public int read(char cbuf[], int off, int len) throws IOException {
        synchronized (lock) {
            ensureOpen();
            if ((off < 0) || (off > cbuf.length) || (len < 0) || ((off + len) > cbuf.length) || ((off + len) < 0)) {
                throw new IndexOutOfBoundsException();
            } else if (len == 0) {
                return 0;
            }

            int n = read1(cbuf, off, len);
            if (n <= 0)
                return n;
            while ((n < len) && in.ready()) {
                int n1 = read1(cbuf, off + n, len - n);
                if (n1 <= 0)
                    break;
                n += n1;
            }
            return n;
        }
    }

    /**
     * Reads a line of text. A line is considered to be started by '[#|'
     * and terminated by '|#]\n'.
     * 
     * @return A String containing the contents of the line, not including any line-termination
     *         characters, or null if the end of the stream has been reached
     * 
     * @see java.io.LineNumberReader#readLine()
     * 
     * @exception IOException
     *                If an I/O error occurs
     */
    String readLine() throws IOException {
        StringBuffer s = null;
        int startChar;

        synchronized (lock) {
            ensureOpen();

            /* Skip to the start of the next log message */
            for (;;) {
                if (nextChar+4 >= nChars)
                    fill();
                if (nextChar+4 >= nChars) { /* EOF */
                    return null;
                }
                if(cb[nextChar] == '[' && cb[nextChar+1] == '#' && cb[nextChar+2]=='|')
                    break;
                nextChar++;
            }
                
            for (;;) {
                if (nextChar+4 >= nChars)
                    fill();
                if (nextChar+4 >= nChars) { /* EOF */
                    if (s != null && s.length() > 0)
                        return s.toString();
                    else
                        return null;
                }
                boolean eol = false;
                char c = 0;
                int i;

                for (i = nextChar; i+3 < nChars; i++) {
                    c = cb[i+3];
                    if (cb[i] == '|' && cb[i+1] == '#' && cb[i+2] == ']' && (c == '\n' || c == '\r')) {
                        eol = true;
                        break;
                    }
                }

                startChar = nextChar;
                nextChar = i;

                if (eol) {
                    String str;
                    if (s == null) {
                        str = new String(cb, startChar, i - startChar);
                    } else {
                        s.append(cb, startChar, i - startChar);
                        str = s.toString();
                    }
                    nextChar++;
                    return str;
                }

                if (s == null)
                    s = new StringBuffer(defaultExpectedLineLength);
                s.append(cb, startChar, i - startChar);
            }
        }
    }

    /**
     * Skips characters.
     * 
     * @param n
     *            The number of characters to skip
     * 
     * @return The number of characters actually skipped
     * 
     * @exception IllegalArgumentException
     *                If <code>n</code> is negative.
     * @exception IOException
     *                If an I/O error occurs
     */
    public long skip(long n) throws IOException {
        if (n < 0L) {
            throw new IllegalArgumentException("skip value is negative");
        }
        synchronized (lock) {
            ensureOpen();
            long r = n;
            while (r > 0) {
                if (nextChar >= nChars)
                    fill();
                if (nextChar >= nChars) /* EOF */
                    break;
                if (skipLF) {
                    skipLF = false;
                    if (cb[nextChar] == '\n') {
                        nextChar++;
                    }
                }
                long d = nChars - nextChar;
                if (r <= d) {
                    nextChar += r;
                    r = 0;
                    break;
                } else {
                    r -= d;
                    nextChar = nChars;
                }
            }
            return n - r;
        }
    }

    /**
     * Tells whether this stream is ready to be read. A buffered character stream is ready if the
     * buffer is not empty, or if the underlying character stream is ready.
     * 
     * @exception IOException
     *                If an I/O error occurs
     */
    public boolean ready() throws IOException {
        synchronized (lock) {
            ensureOpen();

            /*
             * If newline needs to be skipped and the next char to be read is a newline character,
             * then just skip it right away.
             */
            if (skipLF) {
                /*
                 * Note that in.ready() will return true if and only if the next read on the stream
                 * will not block.
                 */
                if (nextChar >= nChars && in.ready()) {
                    fill();
                }
                if (nextChar < nChars) {
                    if (cb[nextChar] == '\n')
                        nextChar++;
                    skipLF = false;
                }
            }
            return (nextChar < nChars) || in.ready();
        }
    }

    /**
     * Tells whether this stream supports the mark() operation, which it does.
     */
    public boolean markSupported() {
        return true;
    }

    /**
     * Marks the present position in the stream. Subsequent calls to reset() will attempt to
     * reposition the stream to this point.
     * 
     * @param readAheadLimit
     *            Limit on the number of characters that may be read while still preserving the
     *            mark. An attempt to reset the stream after reading characters up to this limit or
     *            beyond may fail. A limit value larger than the size of the input buffer will cause
     *            a new buffer to be allocated whose size is no smaller than limit. Therefore large
     *            values should be used with care.
     * 
     * @exception IllegalArgumentException
     *                If readAheadLimit is < 0
     * @exception IOException
     *                If an I/O error occurs
     */
    public void mark(int readAheadLimit) throws IOException {
        if (readAheadLimit < 0) {
            throw new IllegalArgumentException("Read-ahead limit < 0");
        }
        synchronized (lock) {
            ensureOpen();
            this.readAheadLimit = readAheadLimit;
            markedChar = nextChar;
            markedSkipLF = skipLF;
        }
    }

    /**
     * Resets the stream to the most recent mark.
     * 
     * @exception IOException
     *                If the stream has never been marked, or if the mark has been invalidated
     */
    public void reset() throws IOException {
        synchronized (lock) {
            ensureOpen();
            if (markedChar < 0)
                throw new IOException((markedChar == INVALIDATED) ? "Mark invalid" : "Stream not marked");
            nextChar = markedChar;
            skipLF = markedSkipLF;
        }
    }

    public void close() throws IOException {
        synchronized (lock) {
            if (in == null)
                return;
            in.close();
            in = null;
            cb = null;
        }
    }

}
